The Gordon Conference on Second Messengers and Protein Phosphorylation in June, 1990, will concentrate on the regulation of the cell cycle and cell growth by protein phosphorylation, specific protein kinases, and specific protein phosphatases. In the last year explosive progress has been made in understanding the biochemistry of cell cycle regulation, and recently the cdc 2 protein kinase component of MPF has been found to phosphorylate several proto-oncogenes at sties involved in mitotic activation processes. These links between cell cycle and cell growth control provide an interface between membrane events associated with second messenger production, cell cycle dependent kinase activations, and activation of both cytoplasmic and nuclear proto-oncogenes, and oncogenes. The design of the conference will be to examine this interface from varied points of view, including specific protein kinases and phosphatases involved, mechanism of activation/deactivation, and identification of substrates for phosphorylation by mitogen and cell-cycle activated kinases. The conference will present a unique, focused viewpoint lacking in any other conference to date and will provide a lively forum for exchange of information, ideas and prospects for the future. All participants will be encouraged to present posters describing their work. Last year over 80% of the conference participants presented data either in posters or as speakers. Such active participants is a key element in encouraging discussion and fostering new interactions. The sessions planned for the 1990 Conference are: 1) Mitogen-Activated Ser/Thr Protein Kinases; 2) Signalling by Tyrosine Protein Kinases; 3) Protein Phosphatases; 4) Substrate Specificity of Protein Kinases; 5) cdc 2 and Cell Cycle Regulation; 6) Small GTP Proteins; 7) Protein Kinases Regulating Gene Expression; 8) Protein Phosphorylation; 9) Cyclic Nucleotide Phosphodiesterases.